One of the concepts that confuses people most about the Universe is the Earth’s location relative to the Big Bang. People constantly ask, “Where is the center of the Universe?” and “Where was the Big Bang relative to us today?” and perhaps the most articulate of all, “Why does the Cosmic Microwave Background appear in all directions if it came from the Big Bang?” We are creatures accustomed to life in a three dimensional universe, and it is extraordinarily difficult to visualize our place in space. It is even harder to visualize that every place in space was once at the center of the Big Bang. (image credit: NASA/WMAP Science Team)
I have to admit that I’m still building my own personal perspective on the Universe, and every once in a while I still have a mental break through. This is hard. A complete understanding can’t come all at once.
But, being a blogger, I’m going to try and get you as far as I can in one posting.
An excellent starting point is, as always, the Cosmic Microwave Background (CMB). This diffuse microwave signal comes from everywhere and lies behind everything. It was formed at the moment the Universe cooled just enough for electrons to combine with atomic nuclei. Prior to that moment, photons couldn’t travel very far without being absorbed by something and then re-emitted with a new color and/or new direction. After that moment, those photons were set free to travel to us today. That moment was called recombination and it occurred roughly 380,000 years after the Big Bang.
Today, 13.7 +/- 0.2 billion years after the Big Bang, we are seeing CMB photons that originated in a sphere of space around the point that would eventually become the place of the Earth. Similarly, photons that originated at the point where the Earth is now located are possibly being observed by aliens at the location where the photons we are seeing originated. Thus, the CMB photons we see are nothing more than a sphere shaped sample of all the photons released during recombination; they are just one small section of the universe. Think of it this way: Imagine the universe as a giant liquid (it is so big we can’t see its edges to define its shape). A scuba diver hovering within the liquid might be able to illuminate the fluid within 10 feet of his head. The fluid beyond the illuminated sphere is still there. It just can never be seen.
Luckily, the universe isn’t a boring liquid, and the light we see isn’t reflecting off any farthest boring visible point. Unfortunately, the photons we see do come from the farthest visible surface of the universe. Luckily, because the universe was a plasma (which behaves loosely like a fluid), any waves propagating through the early universe will be visible to us. Unfortunately, the waves in the early universe have been stretched out to appearing all but flat with the expansion of the universe. Luckily, we have the technology to discern the 1 part in 10,000 remains of the waves.
And what is magical is this: we can use those waves to determine the shape of the universe. If you stand in a room and sing, you will hear your voice come back to you in different ways depending on the shape of the room. At a certain level, it is possible for good forensic scientists to listen to a recording and determine the shape of the room the recording was made within. At a certain level, it is also possible for good cosmologists to determine the shape of the universe based on the waves within the CMB. What we have learned is this: the geometry of the universe is Euclidean. This means parallel lines stay the same distance apart forever. We also know the universe is likely finite. That means that if a line starts at one point and keeps going for a very very very(!!!) long time, it will eventually get back to where it started, just like a line on the surface of a sphere or a torus.
In fact, a torus is a closed Euclidean shape. Two parallel lines on the surface will always stay the same distance apart and they will eventually circle back to their starting point. It is currently thought that our universe is best visualized as a 4 dimensional hyper-torus.
Here I have to admit, I get the geometry but I can’t actually visualize anything expanding from a singularity - a single point - into a donut.
But this I do understand - I am at the center of the universe. And so are you. And so is everything anyone will ever see with a telescope. At one moment - the first moment - the entire universe was a single point, and that point expanded into everything. Imagine a balloon that when empty is a single point. As you blow it up, the balloon expands. Where on the surface of the balloon is the center of balloon? Everywhere. We are on the surface of a multidimensional universe and every point was at the center. Every point. Even my point and your point.
But there are more issues I have to admit to struggling to comprehend. In the shadowlands at the edge of understanding theorists are looking for evidence of pockets of inflation that went at different rates, or perhaps that simply never stopped expanding. They are looking for evidence of Branes, and probing for variations in gravity.
The CMB is mankind’s first and last best hope for understanding our place in the universe.
A point that grows into a donut? That is hard to grasp. The balloon image makes a lot of sense, but if it’s all surface, is there something inside the balloon? And what’s a brane?
If the universe is shaped like a torus, why is the CMB map shaped like a sphere?
If I had thought for 5 minutes before I asked that… Because it was mapped from earth. From our point of view it looks like the inside of a sphere.
Did I guess right?
The last cosmology that i was able to wrap my head around says that the Universe didn’t start at a point. It was that dense, yes, but it was at least as big as the current visible Universe. That way, there was light, traveling in straight lines, from some bit of the Universe that could be just reaching us now from the CMB. The material that is in our current visible part of the Universe was, at the big bang moment, compressed to the size of a proton, more or less. So the Universe’s real size now is as much bigger than the current visible part of the Universe as the current visible part of the Universe is bigger than a proton. Which is pretty big indeed.
Like the 1907 Bohr model of the atom, with the electrons in neat orbits around the nucleus, i think we’re stuck with such a visualization for the next hundred years. A four dimensional donut is pretty hard to grasp.
It’s a strange universe that we live in. In the news: the local void is pushing the Milky Way. That’s right. This vacuum has so little material in it that it actually is pushing us in a measureable way. That’s repulsive (pun intended). We used to laugh at anti-gravity. And not that long ago.
http://arxiv.org/abs/0705.4139
Ask any parent. They’ve got one or more children who are the center of the Universe. I’m with Copernicus. It’s my son. Did Copernicus have a son? He was a priest, right? But Galileo had a daughter… and he was a priest.
The last cosmology that i could visualize has the Big Bang being very dense. The material that makes up everything in the currently visible part was about the size of a proton. But the Universe, at that density, was at least as big as the currently visible universe. So, the ratio of the size of the currently visible universe to the size of the current universe is at least as large as the ratio of the size of a proton to the size of the currently visible universe. Big indeed.
It’s a strange universe that we live in. In the news: the local void is pushing the Milky Way. That’s right. The local void has so little material in it that it actually is pushing us in a measurable way. The article doesn’t say that, “well, there’s this local void on the one side, and gravity from other stuff on the other side pulls us that way”. It says the local void is pushing us. The other components are accounted for. That’s really repulsive.
We used to laugh at anti-gravity. And not that long ago.
Even though we can and do develop multi-dimensional models, I’ve always felt that we will never be able to fully comprehend the idea because we are limited to 3-dimensional brains. In order to fully comprehend the Universe, we would have to be outside it looking in so that we could grasp it all at once. If we could, then perhaps we would see that we are on the surface of some 3-dimensional shape within a multidimensional world. And as any point on the surface of a sphere would seem to be the center of that surface to an observer at that point, our place in our universe seems to be the center. But in fact, every point on the surface of a sphere could boast the same thing!
Unless we are someday able to escape to one of these other dimensions and look at our three dimensional world (just as we as 3D creatures can comprehend a torus), I don’t think that we can ever fully understand it. I’m not saying that we can’t work with the idea and learn about it, but I just don’t think we can have a truly “gut” feeling about it. Something will always be incomplete — which is good because it means there is always something left to learn!
I tell students not to get frustrated because they can’t “wrap their minds round it,” or just dismiss the idea of other dimensions out of hand because it seems so alien to our everyday existence. Instead, trust the mathematics! The mathematics doesn’t — in my mind at least — guarantee that other dimensions exist, but it at least shows that it is possible.
LS
Pamela … who did the research showing the universe is closed?
Deborah
Interesting topic. I don’t get the idea of 4-D. What’s a torus?
So, in fact, the answer to the question: “Where was the big bang relative to earth?” is “No one knows because too much has happened since then.” This begs the question: Is the Big Bang theory or fact? All too often the “prevailing theory” is treated as fact - a way of thinking that is un-scientific and not conducive to true discovery.
I have not been able to formulate a complete and concise opinion upon the Big Bang. On one hand, quite a bit of scientific findings do support this theory. On the other hand, trying to conceptualize the universe (in all of its’ immensity), beginning from a singularity, is just overwhelming at times. I do understand the mathemathics and geometry with no problem but my finite 3-D perception prohibits me from properly and completely grasping the total concept. I believe that in order to fully grasp the concept you must be able to visualize the whole and not just bits and pieces. I hope and pray that one day humankind will be able to break these bonds of finite thinking and grasp the whole concept of the universe. Until then I cannot help but speculate with the greatest of wonder, what is outside the bubble of the universe? Just something that makes me go “hmmmmm”.
Wow - I stepped away from this sight for a week and you all left so many wonderful comments! I wish there was a way to leave comments in a way that allowed me to interleave my comments with your comments. But… Wordpress has some limitations, so here is one big comment.
First and foremost, let me admit that I mis-spoke. The universe is not closed, but it is likely finite, and in imaging a finite Euclidian universe, I pictured the closed torus and mis-wrote. If that left you confused, wait for tomorrow’s post on the cosmic microwave background, and hopefully I’ll be able to clear things up.
To CTB: A Brane is a confined surface that things can get stuck within in a higher-dimensional universe. In English, a 2-d time cartoon living on a 2-d time piece of paper lives on a 2-d time brane that exists in our at least 3-d time universe. We don’t know how to describe what is inside our outside the geometric surface of our universe – it is beyond testable physics.
To David L: You mostly got it. If you are in a fog and can only see 3 ft in all directions, the boundary of your universe is a sphere with a radius of 3ft. The actual fog bank can be any shape at all. The CMB is our fog bank, and we only see a sphere of it. Everyone only sees a sphere – but we all see a different sphere, just as 5 strangers lost in the fog may never see each other and always see a sphere of fog.
To Stephen: The Void is a complex issue. It doesn’t actually push – it just fails to pull. Please check out this story’s coverage.
To Larry: Somewhere I wonder if there might be an artist afraid of math who thinks visually in 4 or more dimensions as easily as they breath. . .
To Deborah: Corrected that to “likely finite.” Thanks so much for the catch!
To sglasson: A torus is basically a fancy word for a donut. 4-D explains how the surface changes with time. Imagine trying to draw the surface of an expanding balloon as a function of time. You are trying to draw a 4-D surface on a 2-D piece of paper. It just hurts in a mentally good kind of way
To John T; Please take a listen to this and this.
To Fizzlingsynapse: In my mental map, the space outside the universe is labeled “Here be dragons.” It is frustrating to contemplate what we cannot test or observe. We need the magic probe that can tunnel outside of time and space to bring back truth.
It is merely a philosophical construct to conclude that all other vantage points in the Universe would also appear to be a the center, and that the U really has no center. The data itself is equally supportive of the idea that we are at/near the center and other places in the U are NOT at/near the center. And of course that idea is more “normal” to picture in one’s mind. The “problem” with concluding that is that it is “too unlikely” that we just HAPPEN to be at/near the center. It violates the “cosmological/Copernican Principle”. However, that is merely a philosophical concept, rather than something which can be shown true by data. To suggest that we are at such a “special” place in the U goes against an atheistic philosophical world view. Both Hawking and G.T. Ellis have said that there is nothing except philosophy which would cause us to conclude that we were not actually at/near the center of a spherical universe. That is the more parsimonious interpretation to make, unless one has “ruled out God”.
Pam, I’d be interested in your explanation of why we don’t see the same “expanding in all directions” phenomenon in local regions and in small scales. If we can observe it by means of redshift for large scale distances, shouldn’t it be also measurable near us? I’ve heard an explanation of this, but it seemed unsatisfying.
Also, could you address the quantization of redshift? That seems contradictory to the “Universe has no center” view. Thanks.
Here’s my prospective… If a hurricane starts in the atlantic ocean somewhere and we can spot it at the EXACT point where it starts, the we could place the “center”, so to speak. As the hurricane moves is swirls and distorts eventually moving to the carribean somewhere. Now where is the center i ask??? It is where the hurricane is “now”. If one asks,”where was the original center?” Easy, we saw it start and can pinpoint with some very small level of error where it “started”… Now… that’s is what i would concider common 3 dimentional thinking. We saw it start, move and can trace the center through the atmosphere (space). Any can locate the current center because we saw it start. Now let’s add another dimention. What caused the upper-level atmospheric conditions up to this point to make the creation of this initial point? (our concept of the initial starting point) If we as humans are asking when did it all start, Are we asking when the hurricane started or where the hurricane is now?? So in relation to the initial starting point, There will never be a way to say where it started,(we were not there), i just hope that one day we as a human race can eventually find the “eye of the storm” so to speak… time is a wonderful thing to ponder on, i’m happy knowing that i will never know the begining point but i’m ok with that
The center of the universe is relative to every point and we are all at the center.
As the center we never move-or we would no longer be at the center-relative to every point the entire universe must move so if you walk through a room it is the room, the planet and the entire universe that moves not you.
The center of the universe is the present and we are always in the present as is every point, it is time, the present that is relative to every point. Every point is a point of time and the universe and everything in it is made of time itself.
Finally if the point at the center is you then you are every point because every point is at the center.